From mboxrd@z Thu Jan  1 00:00:00 1970
From: Junio C Hamano <gitster@pobox.com>
Subject: Re: Reading commit objects
Date: Tue, 21 May 2013 15:20:47 -0700
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To: Chico Sokol <chico.sokol@gmail.com>
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	(Chico Sokol's message of "Tue, 21 May 2013 18:21:49 -0300")
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Chico Sokol <chico.sokol@gmail.com> writes:

> Hello,
>
> I'm building a library to manipulate git repositories (interacting
> directly with the filesystem).
>
> Currently, we're trying to parse commit objects. After decompressing
> the contents of a commit object file we got the following output:

Who wrote this commit object you are trying to read?  Us, or your
library (this question is to see if you are chasing the right
problem)?

> commit 191
> author Francisco Sokol <chico.sokol@gmail.com> 1369140112 -0300
> committer Francisco Sokol <chico.sokol@gmail.com> 1369140112 -0300
>
> first commit
>
> We hoped to get the same output of a "git cat-file -p <sha1>", but
> that didn't happened. From a commit object, how can I find tree object
> hash of this commit?

If you care about the byte-for-byte compatibility, never use
"cat-file -p".  That is meant for human consumption.

"git cat-file commit <sha1>" gives you the raw representation after
inflating and stripping out the first "<type> SP <length> LF" line.